In communication devices, such as DSL transceivers (DSL: Digital Subscriber Line), it is known to use different power modes so as to allow for power saving in a situation in which not the full capacity of the transceiver is used. For example, according to the ADSL2 specification (ADSL: Asymmetric Digital Subscriber Line) ITU-T G.992.3, three different power modes are known which are referred to as L0, L2, and L3. In the L0 state, the transceiver is operated “full on”, i.e. operating parameters of the transceiver are adjusted in accordance with a maximum allowable bitrate. The maximum allowable bitrate may be limited by the capabilities of the transceiver, by characteristics of a physical communication media connected to the transceiver, or by policies of the network operator. In the L2 state, the operating parameters of the transceiver are adjusted so as to reduce the bitrate as compared to the L0 state. In the L3 state, also referred to as idle state, the transceiver is powered down, which means that data communication is not possible in this state.
According to some applications using DSL communication links, it is desirable that a DSL transceiver is permanently powered on. For example, this may be the case when using VoIP services (VoIP: Voice Over Internet Protocol). Namely, when powering down a DSL transceiver of a subscriber using VoIP services, this subscriber can no longer be reached by a VoIP call. Accordingly, the L3 power mode is not appropriate for some applications. In turn, the L2 power mode is available only in a downstream direction, i.e. in a direction from the network to the subscriber. Moreover, since the L2 power mode involves a reduction of the bitrate, it at the same time also results in increased delays of communicated data. Again, for some applications such as VoIP services, excessive delays are not desirable and therefore, the power saving capabilities of the L2 power mode cannot be fully exploited.
In view of the above, there is a need for efficient power saving techniques in communication devices.